Catheter ablation of AVNRT in children: practical priorities for Australia

Atrioventricular nodal reentrant tachycardia (AVNRT) is a regular supraventricular tachycardia caused by re-entry within or close to the atrioventricular node. In children and adolescents, episodes may present as sudden palpitations, chest discomfort, breathlessness, dizziness, pallor, or unexplained fatigue. Infants can be more difficult to assess, with irritability, poor feeding, diaphoresis, or tachypnoea sometimes providing the only clues.

Catheter ablation has become an established treatment for symptomatic or recurrent AVNRT. The procedure usually targets the slow pathway in the posteroseptal right atrium, with radiofrequency energy or cryoablation used to interrupt the re-entry circuit. In paediatric patients, decisions require careful attention to age, body size, anaesthesia, vascular access, radiation exposure, and the small but important risk of atrioventricular block.

Australian practice is shaped by geography and service concentration. A child from regional Queensland, Western Australia, or Tasmania may travel to Brisbane, Sydney, Melbourne, Adelaide, or Perth for assessment and ablation. Coordinated referral pathways, telehealth review, family accommodation, and communication with local paediatricians help make highly specialised electrophysiology care more accessible.

Recognising AVNRT in children

AVNRT often produces a narrow-complex, regular tachycardia with abrupt onset and termination. Older children may describe a racing heart that starts while resting, during school, or after exercise. Infants and younger children may have sustained rates that are difficult to distinguish from sinus tachycardia without an electrocardiogram. A 12-lead ECG during the episode is valuable, although the rhythm may have stopped before medical review.

The differential diagnosis includes atrioventricular reentrant tachycardia associated with an accessory pathway, atrial tachycardia, atrial flutter, inappropriate sinus tachycardia, and ventricular tachycardia with a relatively narrow appearance. A careful baseline ECG can identify pre-excitation, conduction disease, or structural clues. Echocardiography is generally used to assess cardiac anatomy and function, particularly when the presentation is atypical or there is known congenital heart disease.

Acute management depends on haemodynamic status. Vagal manoeuvres, including an appropriately supervised modified Valsalva technique in older children, may terminate some episodes. Intravenous adenosine is commonly effective when rapid treatment is required and the rhythm is regular. Recurrent emergency presentations, prolonged episodes, medication intolerance, impaired ventricular function, or substantial effects on school and family life may shift the balance towards definitive ablation.

Choosing ablation at the right time

There is no single age at which every child should undergo an electrophysiology study. In an otherwise well adolescent with recurrent symptomatic AVNRT, catheter ablation is often a reasonable first-line definitive option. In a small child with infrequent, well-tolerated episodes, clinicians may initially use observation or antiarrhythmic therapy while considering procedural size, anaesthetic risk, vascular access, and family preferences.

Shared decision-making should include the likely benefits and limitations of both treatment paths. Ablation can remove the need for long-term medication and reduce unscheduled presentations, but it involves anaesthesia, venous catheterisation, and a recognised risk of recurrence or conduction system injury. Medication may control episodes without an invasive procedure, yet adherence, side effects, and breakthrough tachycardia can remain significant concerns.

For Australian families, practical circumstances often affect timing. A family travelling from Darwin or a remote Western Australian community may prefer a single comprehensive visit in a metropolitan centre, while a family living near Melbourne or Sydney may have easier access to repeat reviews. Public hospital waiting lists, private health insurance arrangements, parental leave, school attendance, and the availability of local emergency care should be discussed without allowing logistics to replace clinical judgement.

Mapping and energy strategies

During an electrophysiology study, catheters are introduced through venous access and positioned to record atrial, His bundle, and ventricular activity. Programmed stimulation is used to establish dual atrioventricular nodal physiology and reproduce the clinical tachycardia when possible. The operator then maps the slow-pathway region, generally near the coronary sinus ostium and the lower right atrial septum.

Radiofrequency ablation provides durable treatment with high acute success in experienced centres. Its principal concern is collateral injury to the fast pathway or His bundle, leading to complete atrioventricular block and possible permanent pacing. The risk is low, but its consequences are serious, particularly in a child who may otherwise have many decades of device follow-up ahead.

Cryoablation is attractive in paediatric electrophysiology because cryomapping can test the effect at a target site before a permanent lesion is delivered. If conduction changes occur during test freezing, the catheter can be rewarmed and repositioned. Cryotherapy may be associated with a lower perceived risk of permanent atrioventricular block, although recurrence can be somewhat higher in some series. The choice depends on anatomy, operator experience, equipment, and the child’s individual risk profile.

Three-dimensional electroanatomical mapping and low- or zero-fluoroscopy techniques can reduce radiation exposure. This matters for children because radiation effects are cumulative over a lifetime. Fluoroscopy may still be used when clinically necessary, especially in complex anatomy, but modern laboratories can often minimise exposure through careful imaging protocols and intracardiac electrogram guidance.

Managing safety and special anatomy

The most important procedural complication is inadvertent atrioventricular block. Operators monitor His bundle signals, local electrograms, junctional rhythm, and changes in atrioventricular conduction throughout energy delivery. A transient junctional rhythm during slow-pathway ablation may be expected, but loss of conduction or concerning catheter stability requires immediate reassessment.

Other complications include vascular injury, haematoma, pericardial effusion, thromboembolism, infection, arrhythmia induction, and anaesthesia-related events. These are uncommon, but families should receive a clear explanation of warning symptoms after discharge, including persistent chest pain, syncope, fever, limb swelling, bleeding, or recurrent sustained palpitations. Children who have had previous surgery, venous obstruction, or complex congenital heart disease may require modified access and advanced imaging.

Anaesthesia planning is especially relevant in younger patients. Tachycardia may be difficult to reproduce under general anaesthesia, while light anaesthesia can produce movement and affect procedural conditions. A paediatric anaesthetist, electrophysiologist, and nursing team should agree on medication management, fasting instructions, vascular access, temperature control, and recovery arrangements.

Long-term device consequences also deserve perspective. Permanent pacing is rarely required after uncomplicated AVNRT ablation, yet any child who does require a pacemaker enters a separate pathway of lifelong surveillance. Lessons from broader device care, including lead fracture management, reinforce the importance of structured interrogation, reliable transition arrangements, and prompt assessment of abnormal device alerts.

Follow-up across Australian services

After ablation, most children can leave hospital the same day or after overnight observation, depending on age, comorbidity, access-site concerns, and local policy. A follow-up ECG confirms rhythm and conduction, while ambulatory monitoring is reserved for persistent symptoms, uncertain procedural success, or suspected recurrence. Families should know that brief isolated extra beats do not necessarily indicate return of AVNRT.

Recurrence is usually related to incomplete or recovered slow-pathway conduction. It may occur early or months after the procedure. A documented rhythm strip is more useful than a symptom description alone, so families can be encouraged to seek an ECG during significant episodes where practical. Smartwatch recordings may sometimes support triage in adolescents, but they do not replace a diagnostic 12-lead ECG or clinical assessment.

Follow-up should connect the tertiary electrophysiology service with the child’s general practitioner, paediatrician, and local cardiology team. In Australia, telehealth can reduce repeated long-distance travel, although an in-person assessment remains important when symptoms are recurrent or the ECG is abnormal. Families should also receive advice about returning to school, swimming, sport, and normal activity, with restrictions tailored to access-site recovery and any underlying cardiac condition.

A broader systems approach is useful when evaluating post-procedure care. Research on readmission predictors in other ablation populations highlights the value of discharge education, early contact, medication reconciliation, and clear escalation pathways. These principles are applicable to paediatric services even though AVNRT generally has a different risk profile from atrial fibrillation.

Evidence, training, and publication

Reported acute success rates for paediatric AVNRT ablation are high, while major complications are uncommon in experienced centres. Interpretation requires attention to patient age, follow-up duration, energy source, mapping technology, and the definition of recurrence. Results from adult populations cannot simply be transferred to infants or small children, whose anatomy, anaesthetic requirements, and lifetime exposure to procedural risk differ.

Australian clinicians must also account for local governance and consent requirements. Parents or legal guardians generally provide consent for younger children, while adolescents should be involved in decisions in a developmentally appropriate way. The mature minor principle may be relevant in some circumstances, and state or territory law, hospital policy, and ethics guidance should be considered. Devices and procedural equipment must fit local procurement pathways and applicable Therapeutic Goods Administration requirements.

Training opportunities are concentrated in specialist cardiac centres, making case review, simulation, proctored procedures, and collaboration across the Asia-Pacific region particularly valuable. Researchers can strengthen the evidence base through prospective registries that record age, weight, anatomy, ablation energy, radiation dose, recurrence, conduction outcomes, patient-reported symptoms, and access to follow-up. Consistent reporting would help compare strategies across metropolitan and regional referral networks.

Clinicians and investigators developing studies, reviews, or technical reports can consult the journal’s author guidelines before preparing a submission. Well-designed paediatric electrophysiology research can inform procedural counselling, improve safety standards, and clarify how cryoablation, radiofrequency ablation, and low-radiation mapping should be selected for different age groups.

Catheter ablation offers many children with symptomatic AVNRT a durable return to ordinary activity, but success depends on more than terminating the arrhythmia. Careful diagnosis, age-appropriate consent, experienced mapping, meticulous conduction monitoring, and accessible follow-up are central to safe practice. Australian paediatric and adult congenital services can help families move from emergency treatment to definitive rhythm care through coordinated referral, transparent counselling, and evidence-led procedural planning. Publish and share high-quality clinical experience through the Journal of Arrhythmia to support safer electrophysiology for children across Australia and the wider Asia-Pacific region.